Feeding difficulties and airway-related complications in neonates, which contribute significantly to the infant mortality and morbidity with enormous socioeconomic consequences, might be related to motor functions of pharynx, esophagus, or stomach which may be dependent upon neural control and muscular function. Prematurity, perinatal asphyxia, and congenital abnormalities represent three important contributory factors to feeding difficulty among infants, who fail to thrive and chronically suffer from nutritional deprivation, gastroesophageal reflux, in addition to chronic lung disease and other life-threatening events. Our long-term objective is to define the mechanisms of feeding failure and airway compromise in developing infants, to pave way for evidence-based diagnosis and therapeutic intervention. Specific Aim 1 will determine maturational changes in the relationship between deglutition and airway safety. We will evaluate the basal and protective motor mechanisms involved in pharyngeal and esophageal phases of swallowing in developing infants during health and disease. Specific Aim 2 will investigate the mechanisms of esophageal and airway protection or compromise in infants with congenital foregut anomalies and neurologic disorders. Using well-established techniques developed at our Center, the innovative micromanometric water perfusion technique and a specially designed micromanometric catheter with sleeve sensor, we will measure pressure relationships at various levels within the foregut. Respiratory function measurements will simultaneously be recorded to to establish the relationship between esophageal motility and respiratory function in health and disease, and to ensure subject safety. In addition to ANOVA for repeated measures and students t-test, we will use growth curve analysis with a logistic model to permit the use of longitudinal grouped data. These studies will establish improved basal and protective esophageal motor function with development, and identify mechanisms of feeding failure and airway safety in infants.